Colombia's president Juan Manuel Santos greets US vice president Mike Pence after a press conference in Cartagena, Colombia on August 13, 2017. Colombian Presidency/Handout via Reuters

The United States "will not stand by as Venezuela crumbles", vice president Mike Pence said on Sunday, even as he emphasised a peaceful path while standing by president Donald Trump's startling warning that US military action remained a possibility.

"We have many options for Venezuela, but the president also remains confident that working with all of our allies across Latin America we can achieve a peaceable solution," Mr Pence said in a news conference alongside Colombian president Juan Manuel Santos, as he began a week-long Latin America tour of four countries.

His trip comes after Mr Trump on Friday said he was mulling a range of scenarios for crisis-hit Venezuela "including a possible military option if necessary".

Mr Trump's comment drew condemnation from Caracas, which called the threat "reckless" and "craziness".

The rest of Latin America — even countries strongly opposed to Venezuelan president Nicolas Maduro's usurpation of his country's democratic institutions — also strongly rejected it.

Mr Santos re-affirmed that regional stance by saying he told Mr Pence frankly "that the possibility of a military intervention shouldn't even be considered".

"The Latin American continent, every country in Latin America, would not favour any form of military intervention," he added.

Colombia, Venezuela's neighbour, is a stalwart US ally and a fierce critic of Mr Maduro and his policies.

But Colombia and many other Latin American countries have bitter memories of past US adventures in the region, including invasions, the propping up of military dictators and the sponsorship of guerrilla groups and paramilitaries.

Mr Pence's trip to Colombia, Argentina, Chile and Panama was dominated by US efforts to find joint action with Latin American partners to increase pressure on Mr Maduro.

Washington has already imposed unilateral sanctions on Mr Maduro and nearly two dozen of his officials over the establishment of a new loyalist body, an all-powerful Constituent Assembly, that supersedes the legislature controlled by the opposition.

Addressing the threat of military action, Mr Pence said: "President Trump is a leader who says what he means and means what he says."

But he emphasised his trip was "to marshal the unprecedented support of countries across Latin America to achieve by peaceable means the restoration of democracy in Latin America, and we believe it is achievable by those means".

Mr Trump's stated possibility of a US military operation looked likely to shadow Mr Pence at every stop, eclipsing bilateral issues, especially trade, that he was raising along the way.

In Venezuela, Mr Maduro's regime has seized onto Mr Trump's threat as proof of its oft-repeated claim that the US wanted to topple the current leftist government to get its hands on Venezuela's oil reserves, the largest in the world.

The Venezuelan opposition coalition seeking to oust Mr Maduro through early elections on Sunday also rejected "the use of force, or the threat of applying such force, by whatever country against Venezuela", it said in a statement.

Venezuela's leftist allies Bolivia, Cuba, Ecuador and Nicaragua meanwhile all supported Venezuela in a confrontation against its "imperialist" foe.

Venezuela's economy is heavily reliant on its oil exports, and shipments to the US — its biggest customer — account for 40 per cent of its crude production, but only eight per cent of American oil imports.

The US sanctions so far have been against individuals and not targeted at Venezuela's oil industry, which would have consequences for US refineries.